Lifecasting is the process of taking a mold directly from a models body and creating a sculpture using that mold. A casting material is placed into the mold and when cured, you have an exact duplicate of the body part that you molded. Molds can be made from a variety of materials such as plaster bandages, alginate, skin safe silicone and more. There is also a wide variety of casting materials; fiberglass, gypsum products, etc.
The first step in lifecasting is to decide on a pose. The model will have to maintain that pose for approximately 25 to 30 minutes so steps should be taken to assure their comfort. If my model is standing I usually have them lean against a sloped backboard. If the model is lying down, a rolled towel or cushion can be used for support under the neck, legs or where needed.
Because you want your model to be freed from the mold without pulling bodyhair or skin, a release agent is applied to the skin. Next apply the molding material to the models body. When the mold material hardens, it is removed from the models body and ready to cast. Below are a few photos of the actual process.

In the photo below the pose was predetermined and a release agent was applied to the model. This mold was cast in several sections to facilitate removal of the plaster bandages when they harden.

Because this is a large mold, strips of wood are plastered into position for strength.

Skin safe silicone rubber was applied to the models face with her nostrels left uncovered so she could breath. This rubber was backed up with plaster bandages so the soft rubber would maintain its' shape. The same process was used to mold the feet and hands.

The photo below shows the cast after several of the sections have been seamed together.